Two-color or three-color injection molding processes have been practiced, in which a mold is turned from side to side in order to receive two or three injection streams one after another from the injection nozzles; the product frame built from the beginning is filled with each colored resin at a selected area. There is another known process in which two-colored resins individually molten in two injection units are independently and simultaneously injected through one nozzle to form a color pattern. There is still another process of sandwich molding in which two resins different in kind are successively injected through a common sprue out of separate injection units.
Multi-color molded products with intricate designs for a high decorative effect are in demand. The conventional molding process and machine, however, cannot make a three-dimensional appearance of complex or intricate multi-color patterns with more than three colors.